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Node.js Express Best Practice
===

###### tags: `Node.js` `Express` `best practice`

> [name=Shueh Chou Lu][time=Dec 17, 2020]

---

[TOC]

---

## Do In Code

1. Compression: proxy > app.use(compression())
2. Asynchronous (async.) >> Synchronous (sync.)
- The **only** reason to use sync. function is the time to start up server.
唯一有理由使用同步函數的時機是在最初啟動之時
3. Static files: proxy > serve-static > res.sendFile()
4. Console is sync! Always use async or use sync only in development.
- Debugging: debug >> console
- Application: Winston / Bunyan >> console
5. Handle Error ( Important!, Detail in next section )
- Try-catch
- Promise

## Handle Error

1. Try-catch is **synchronous**.
2. Express catch all sync. error in default (v.5 catch *Promise* as well)

### What will log?

const callback = async () => {
  console.log('do another thing');
  throw new Error('foo');
  console.log('do more thing');
}

const method = async () => {
  console.log('do first thing');
  await callback();
  console.log('do second thing')
}

const main = async () => {
  try {
    await method();
  } catch (err) {
    console.log('fire try-catch!');
  }
  
  console.log('finish project!');
}

#### result:

do first  thing
do another thing
do second thing
finish project!
UnhandledPromiseRejectionWarning: Error: foo
... (error stack)

#### why?

1. `callback` invoked some time later after `method` (`do another thing`)
2. happend exception! wait to finish other process
3. finish method (`do second thing`)
4. finish try-catch block
5. final run (`finish project!`)

### Category

1. Operational Errors
- The errors you are/can except.
- Log, Show, Retry/Abort.
2. Programmer Errors
- [The best way to recover from programmer errors is to crash immediately](https://www.joyent.com/node-js/production/design/errors#fnref:1)
- Try debug your program rather than handle it.

## Do In Configuration

1. `env.NODE_ENV='production';`
2. Rebuild after error, use [helpers](http://strong-pm.io/compare/) or *init* system [[1]](https://wiki.debian.org/systemd)[[2]](http://upstart.ubuntu.com/)
3. Multi-threads [[1](https://nodejs.org/docs/latest/api/cluster.html)][[2](https://docs.strongloop.com/display/SLC/Clustering)]
4. Caching [[Varnish](https://www.varnish-cache.org/)][[Nginx](https://serversforhackers.com/nginx-caching/)]
5. Reverse-Proxy [[Nginx](https://serversforhackers.com/nginx-caching/)][[HAProxy](http://www.haproxy.org/)]

## PPT

https://drive.google.com/file/d/1JW7Ec81uUgPyfMFr3a6ZK9H1r7OHGqhp/view?usp=sharing